The present invention relates to the field of wireless communication. More specifically, the present invention relates to the field of wireless simplex packet communication.
There is a considerable need for dispatch communications, i.e., simplex bi-directional communications between a dispatcher and remote (field) units. This need is conventionally filled by specialized equipment operating over dedicated frequencies. Examples of this type of equipment are the dispatch radios used by police, fire, ambulance, taxi, and delivery services. In dispatch systems, a single dispatch unit typically uses one frequency (frequency xe2x80x9cAxe2x80x9d) for transmission and another frequency (frequency xe2x80x9cBxe2x80x9d) for reception, with all field units using frequency xe2x80x9cBxe2x80x9d for transmission and frequency xe2x80x9cAxe2x80x9d for reception.
Dispatch radios share many problems with other simplex systems, e.g., construction-site walkie-talkie radios, personal-service radios, and other business radios. In such systems, all units typically use a single frequency for both transmission and reception. By necessity, the number of units in such systems is severely limited.
Such communication systems are often simplex. That is, a given unit may only transmit or receive at one time, but not both. This limitation is both a weakness and a strength of such systems. Since only one unit of a communicating pair may be transmitting at one time, interruptions are impossible, regardless of the urgency involved. On the other hand, the equipment need not have the complexity and expense of full duplex communication equipment. Because of their similarities, dispatching and single-frequency systems may be generally classed as push-to-talk (PTT) systems for the purposes of this discussion.
PTT systems suffer from a significant number of problems. A major one of these problems is that PTT systems are typically proprietary. That is, the equipment for a given system is often made by a single manufacturer. This obliges the user/owner to deal with this single manufacturer. The equipment is therefore often more expensive than similar equipment for other services, even though that other equipment may be more sophisticated than the needed equipment. The reasons for this are complex, involving the scale of production as well as the lack of competition.
Similarly, such equipment often must be serviced by specially trained and licensed personnel. Again, being a small market, a given area will often have only a small pool of qualified service agencies/personnel. Such an agency is typically licensed or certified by the manufacturer. This again leaves the user/owner at the mercy of the manufacturer through the service personnel, resulting in a decrease in competition and an increase in service expenses.
Because such PTT equipment is often manufactured and serviced by a single company, the user/owner may well be left without support of any kind should that manufacturer cease to do business. Alternatively, the user/owner of the equipment may be faced with a considerable difficulty should the local service agency of the equipment manufacturer cease to represent that manufacturer. This often necessitates that the equipment be returned to the manufacturer for servicing, thereby effecting unreasonable delays.
PTT systems are typically manufactured to fulfill specific and unique requirements. That is, while the PTT dispatch system used by a taxicab company is similar in design and function to that used by a fire department, they are designed to operate at different frequencies and are not interchangeable. This non-interchangeability extends beyond physical constraints and into the areas of licensing and legislation. Therefore, a small rural volunteer fire department on a tight budget is constrained from using donated taxi dispatching systems. The systems and their components are not interchangeable.
Because of this incompatibility of hardware and operating frequencies, two different PTT systems cannot readily intercommunicate. For example, in an emergency situation it may be desirable to coordinate police, fire, and medical field units from a single dispatching unit. This is not normally feasible without a special cross-service dispatching unit and/or multiple dispatching units in the same location. Overcoming such incompatibilities increases the expense of each of the systems while being an inefficient compromise at best. Additionally, the use of such a centralized and complex dispatching center often necessitates the use of a highly skilled and specially trained dispatcher (operator). This, too, increases system expense.
PTT systems typically operate within specific frequency bands by law. These bands have limited capabilities, thus creating a problem when many services must use the same band. Since each PTT system providing a given class of service, e.g., taxicab dispatching, must share the same band while simultaneously utilizing different channels (frequency allocations with the band), such channels are often at a premium in large metropolitan areas. Occupation of all available channels in a given area would prohibit the assignment of another channel in that area. Therefore, a potential new user may be inhibited from receiving a needed license.
Likewise, since a shortage of channels may produce a waiting list for licenses, the loss of a license for a given channel, however briefly and for whatever reason, may result in the assignment of that specific channel to a new licensee, thereby effectively driving the former license holder out of business.
PTT systems also have coverage problems. Not only does the specific equipment have an operating range limited by design, the operating range is also limited by geography. For example, operation is typically limited to xe2x80x9cline-of-sightxe2x80x9d for the frequencies and signals involved. Shadows may thereby be cast by natural and artificial geography. In a typical scenario, for example, a taxicab dispatching service may lose contact with any cab in an area shadowed by a hill. Similarly, a messenger service may have only intermittent and unpredictable contact with messengers in a downtown area due to a large number of steel and concrete buildings. Both problems derive from the very structure of a PTT dispatching system. That is, all mobile field units must communicate with a fixed dispatching unit via an electromagnetic line-of-sight. Therefore, if the geophysical relationship between the field unit and the dispatching unit is such as to inhibit transmission and/or reception, then communication is lost.
Dispatching systems make up a significant portion of PTT systems in use. PTT dispatching systems typically have a single dispatching unit and a plurality of field units. As previously mentioned, the dispatching unit may transmit on frequency xe2x80x9cAxe2x80x9d and receive on frequency xe2x80x9cB,xe2x80x9d while the field units transmit on frequency xe2x80x9cBxe2x80x9d and receive on frequency xe2x80x9cA.xe2x80x9d This means that a PTT dispatching system has an assigned dispatching unit that differs in kind as well as operation from the field units.
The centralized dispatching unit of a PTT dispatch system typically transmits to all field units simultaneously. That is, a typical two-frequency PTT dispatching system cannot readily communicate to only a subset of the assigned field units. There are systems in which selective dispatching is implemented, but all such systems are expensive and inefficient. For example, each field unit may have an address affixed to the beginning of each dispatch intended exclusively therefore. The use of such an address header therefore allows private messages to be dispatched. However, this increases radically in complexity when multiple (but not all) field units are to be addressed.
In an alternative dispatching scheme, the centralized dispatching unit may have multiple transmission frequencies. This allows normal dispatches (i.e., those intended for all field units) to be transmitted on a first frequency with selective dispatches being transmitted on a second frequency. In this scheme, the dispatcher would instruct the appropriate field units to switch to the second frequency prior to the transmission of a selective dispatch. However, this scheme requires an increase in complexity in both the dispatch and field units, including the incorporation of a switching mechanism with a corresponding decrease in reliability.
The complexity of dispatching to selected units using known conventional dispatching schemes increases dramatically when the number and addresses of the selected units is dynamic. In a highly dynamic emergency situation, for example a forest fire, the xe2x80x9cgroupsxe2x80x9d to be addressed may change many times in the course of the emergency as personnel move from one location to another. Conventional dispatching systems simply lack the flexibility to change fast enough to optimize the dispatching. Rather, under most such dynamic situations, the dispatcher is reduced to general all-unit dispatching only.
There are many circumstances when general all-unit dispatches are less than optimal. For example, peace officers may be making a covert entry into a building. The last thing desired in such a situation is a sudden outburst over the radio. Selective dispatching, therefore, should not only be capable of easily and efficiently dispatching to only selected field units, it should be capable of easily and efficiently not dispatching to selected field units. This is not easily accomplished with currently available PTT dispatching systems.
Another problem exists with conventional PTT dispatching systems in that multi-level dispatching is not practical without exceptionally complex equipment and/or operations. In a multi-level dispatching scheme of four levels (e.g., headquarters, groups, teams, field units), an overall dispatcher at headquarters would be capable of dispatching down directly to all group dispatchers, team dispatchers, and field units. Each group dispatcher would be capable of dispatching down to all team dispatchers and field units within that group, and up to the headquarters dispatcher. Each team dispatcher would be capable of dispatching down to all field units within that team, up to the group dispatcher for that team, and (optionally) up to the headquarters dispatcher. Each field unit would be capable of dispatching up to the team dispatcher for that team, (optionally) up to the group dispatcher, and (optionally) up to the headquarters dispatcher. Such a xe2x80x9cchain of commandxe2x80x9d structure is ideal for coordination during major emergencies (such as earthquakes or floods), but cannot be readily realized with conventional PTT dispatching services without the complexity and expense of military-type equipment.
The dispatching unit of a PTT system is different in kind to the field units. The dispatching unit is typically a fixed xe2x80x9cbase station.xe2x80x9d As such, the dispatching unit is tied to mains service and is not mobile. This causes PTT dispatching systems to be severely handicapped during fluid situations where the base station may be lost. To cover for such circumstances, a xe2x80x9cmobile base unitxe2x80x9d may be used, typically an alternative base station mounted in a truck or other vehicle. Such a mobile base station adds significantly to the overall expense of a PTT system. The expense involved often drives such a feature beyond the range of small communities who, ironically, may best benefit from it.
Again, because the dispatch unit of a PTT dispatch system is inherently different than a field unit, a field unit cannot normally be used as an alternative dispatch unit in the event of failure of the dispatch unit. Therefore, the integrity of the entire system depends upon the integrity of a single dispatch unit. Should the dispatch unit fail, the entire system fails. This poses a less-than-optimal situation when the PTT dispatch system is critical, necessitating the acquisition of a second dispatch unit whose sole function is to stand by in case the primary dispatch unit should fail. Again, this represents a waste of resources.
Where the PTT dispatch system is less critical, the failure of the dispatch unit causes the system to be inoperative while the dispatch unit is repaired or replaced. This necessitates the use of alternative communications (e.g., telephones), which provide an awkward solution at best.
The field units in some PTT dispatch systems do not normally have the ability to intercommunicate. That is, the field units in a system normally all transmit on frequency xe2x80x9cBxe2x80x9d and receive on frequency xe2x80x9cA.xe2x80x9d No field unit can then receive the transmission from another field unit. This lack of intercommunication necessitates that a typical field unit may convey information to another field unit only through the dispatch unit. This places an additional burden upon the dispatcher and slows down the conveyance of intelligence, making coordinated efforts more difficult.
Certain types of specialized field units have the ability to transmit and receive upon alternative frequencies. When this ability is engaged, those specific field units effectively are removed from the PTT dispatch system and become a local single-frequency PTT system. This condition poses the potential of a serious problem during a crisis situation. While the needed and necessary local intercommunication is enabled, those field units are inhibited from receiving information from the dispatch unit. Such information may be critical e.g., the inability of expected backup to arrive when planned.
Another problem exists with conventional PTT dispatching system in that, other than by direct query and extrapolation therefrom, the dispatcher has no way of knowing the locations of the field units. This means that, even if sophisticated multi-channel equipment is used, the dispatch unit cannot readily transmit a zone dispatch, i.e., a dispatch to all units within a specific geographical area. During a crisis, considerable effort is expended for the sole purpose of keeping track of the individual field units. This effort often entails several people and a considerable amount of traffic for location determination. Such an ability, totally lacking in conventional PTT dispatching systems, would be invaluable coordinating even a small crisis (e.g., the coordination of taxicabs with the near-simultaneous arrival and departure of several major flights during a rush hour).
Conventional PTT dispatching systems often lack in system security. Such systems typically use conventional amplitude or frequency modulation (AM or FM) utilizing analog (i.e., non-digital) modulation techniques. This approach, while cost-effective, is very insecure and does little to inhibit eavesdropping.
A courier service, for example, depends heavily upon its established customer base for survival. Were an unscrupulous competitor to eavesdrop upon the courier service""s dispatches for a relatively short period of time, that competitor might then be in a position to determine the courier service""s major clients and the number of pick-ups and deliveries per week. With this information, the competitor may be able to successfully underbid the courier service for those clients.
In a similar but more critical vein, were an unscrupulous press able to monitor police dispatches during a major crisis, important information may be leaked that would jeopardize negotiations and perhaps cost lives.
One answer to the eavesdropping problem is to encrypt the information. This is a straightforward procedure in digital systems, but somewhat cumbersome and expensive in analog systems. While encryption can be successfully used in critical PTT dispatching services (police, fire, etc.), it is often cost-prohibitive for business systems.
Attempts to substitute for encryption often involve the use of elaborate codes. Such codes may require considerable training, hence expense, and are far from foolproof. A single disgruntled employee or lost/stolen codebook is all that is needed to compromise such a code.
In addition, a fundamental failing of conventional PTT systems is an inability to interface with the outside world. This lack of interface means an inability to place a telephone call through the system without involving the dispatcher. This type of situation may arise, for example, should an individual field employee (an employee with a field unit) be awaiting the results of a medical test for him/herself or a family member. The employee is faced with three choices. The employee may have the doctor or laboratory contact him/her through the system (in violation of individual privacy rights). The employee may stop and call the doctor or laboratory repetitively from a telephone until the results are available (inconvenient to both the employee and the employer). Or the employee may stay at home until the results are available (even more inconvenient and a loss of income to both the employee and the employer)
Associated with this lack of outside-world interface is the inability to summon emergency services when seconds may count. This inability may directly endanger lives and/or property.
With the proliferation of cellular telephone service, the replacement of PTT systems with cellular telephone systems is now possible. Unfortunately, the use of standard cellular telephone systems in lieu of PTT systems is not easily accomplished.
The first problem encountered when replacing a PTT system with a cellular telephone system is that of overkill. The replacement of a simplex communication system with a full-duplex system represents a significant waste of resources. Not only must adequate bandwidth for full duplex communication be allocated, it often must be allocated for the full duration of the conversation, i.e., from the time the connection is made until the parties hang up. These inefficiencies are a result of the circuit-switched services of cellular telephony, and are directly translatable into fiscal losses.
Additionally, the call time for a cellular telephone service is significantly greater than that of a PTT service for a given message. Again, this is due to the active set up time needed for each call, and also for the fact that a cell phone""s transmitter must occasionally transmit even when the phone is only receiving. This excess of transmission leads to a shorter battery life than desired.
Another problem is that, since a cellular telephone system is capable of calling any other telephone anywhere in the world, it uses a dialing scheme essentially the same as the traditional wire-based telephone system. Therefore, even with one-button dialing, there is a considerable time between the commencement of dialing and the completion of the connection so that communication may occur. This delay, while small for any single call, quickly becomes unmanageable when the standard cellular system is used as a PTT dispatching system replacement.
What is needed therefore, is a system that is broad in functionality, is wide in area of coverage, is easily accessible, is pervasive, requires no special licenses, requires no special equipment, is inexpensive to use, has the flexibility of the global cellular telephone system, and has the rapidity and ease of use of a conventional PTT dispatching system.
Accordingly, it is an advantage of the present invention that an improved system for dispatching information packets and a method therefore is provided.
It is another advantage of the present invention that a simplex PTT communication system is provided utilizing a conventional (non-proprietary) cellular telephone system.
It is another advantage of the present invention that a PTT cellular communication system is provided that allows inter-system communication without the need of specialized equipment.
It is another advantage of the present invention that a PTT cellular communication system is provided that utilizes a plurality of transmission points in a given area, thus minimizing shadowing.
It is another advantage of the present invention that a PTT cellular communication system is provided that permits selective dispatching (i.e., dispatching to a single field unit or a selected group of field units) without specialized equipment.
It is another advantage of the present invention that a PTT cellular communication system is provided that permits silent (text) reception of a voice dispatch.
It is another advantage of the present invention that a PTT cellular communication system is provided that inhibits eavesdropping.
It is another advantage of the present invention that PTT cellular communication system is provided that permits traditional incoming and outgoing telephone calls over the same equipment.
It is another advantage of the present invention that a PTT cellular communication system is provided that utilizes conventional cellular systems while effectively eliminating dial-up delay.
The above and other advantages of the present invention are carried out in one form by a method of simplex information-packet dispatching utilizing a telecommunication network. The method contains a transmitting activity wherein an information packet containing a voice frame from an origination unit is transmitted. The method also contains a routing activity wherein the information packet is routed via the telecommunication network utilizing a wireless non-circuit-switched service thereof. The method also contains a receiving activity wherein the information packet is received at a destination unit.
The above and other advantages of the present invention are carried out in another form by a system for simplex dispatch of an information packet utilizing a telecommunication network. The system incorporates an origination unit configured to generate the information packet to contain a voice frame and to transmit the information packet via a wireless non-circuit-switched service of the telecommunication network, wherein the information packet is configured as an origination packet when within the origination unit. The system also incorporates a destination unit coupled to the origination unit via the telecommunication network and configured to receive and present the information packet, wherein the information packet is configured as a destination packet within the destination unit.
A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference numbers refer to similar items throughout the Figures, and:
FIG. 1 shows a block diagram depicting a system for dispatching an information packet in accordance with a preferred embodiment of the present invention;
FIG. 2 shows a graphic representation of an origination packet in accordance with a preferred embodiment of the present invention;
FIG. 3 shows a graphic representation of a destination packet having a voice frame in accordance with a preferred embodiment of the present invention;
FIG. 4 shows a graphic representation of a destination packet having a text frame in accordance with a preferred embodiment of the present invention;
FIG. 5 shows a graphic representation of a destination packet having both a voice frame and a text frame in accordance with a preferred embodiment of the present invention;
FIG. 6 shows a flow chart depicting a process for dispatching a simplex information packet in accordance with a preferred embodiment of the present invention;
FIG. 7 shows a flow chart depicting a subprocess for generating an information packet in an origination unit in accordance with a preferred embodiment of the present invention;
FIG. 8 shows a block diagram depicting an origination unit of an information-packet dispatching system in accordance with a preferred embodiment of the present invention;
FIG. 9 shows a flow chart depicting a subprocess for routing an information packet from an origination unit to a server in accordance with a preferred embodiment of the present invention;
FIG. 10 shows a flow chart depicting a subprocess for converting an information packet from an origination packet to a destination packet in accordance with a preferred embodiment of the present invention;
FIG. 11 shows a block diagram depicting a server of an information-packet dispatching system in accordance with a preferred embodiment of the present invention;
FIG. 12 shows a flow chart depicting a subprocess for routing an information packet from a server to a destination unit in accordance with a preferred embodiment of the present invention;
FIG. 13 shows a flow chart depicting a subprocess for presenting the contents of an information packet to a recipient in accordance with a preferred embodiment of the present invention; and
FIG. 14 shows a block diagram depicting a destination unit of an information-packet dispatching system in accordance with a preferred embodiment of the present invention.